You should implement Captcha in the be.5ch.net registration form or set up a managed challenge with Cloudflare WAF for the entire be.5ch.net. Then you can easily ban bots by simply setting "BBS_BE_ID=1" on a board that is being indiscriminately trolled by bots.
However, in order to prevent confusion among users, the BBS must be notified when setting it.
It is most easy way.